BFNA Title: Chryso-hypnum
Author: W. R. Buck
Date: July 24, 2009
Edit Level: R
Version: 1

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden

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XX. CHRYSO-HYPNUM Hampe, Bot. Zeitung (Berlin) 28: 35. 1870

William R. Buck


Mittenothamnium sect. Pseudo-microthamnium (Brotherus) Wijk & Margadant


Plants mostly small, sometimes medium-sized, in soft, dark-green to golden, often extensive, dense mats. Stems creeping, prostrate, with rhizoids all along the underside, freely and irregularly to regularly pinnately branched, the branches mostly simple, short, blunt, densely foliate; in cross-section without a hyalodermis, with small thick-walled cells surrounding larger thinner-walled cells, central strand small or absent; pseudoparaphyllia foliose; axillary hairs with 1--3 short brown basal cells and 1--2 +/- elongate, hyaline, brown distal cells. Leaves of stems and branches similar, erect- to wide-spreading, soft, mostly ovate, +/- abruptly short- to long-acuminate, sometimes concave, seldom plicate, not or scarcely decurrent; margins serrulate, often throughout, plane to erect or recurved; costa short and double; cells linear, prorulose at distal and sometimes proximal ends abaxially, rarely smooth, often firm-walled, becoming shorter and broader toward the insertion; alar cells few in extreme angles, quadrate to short-rectangular. Specialized asexual reproduction none. Sexual condition mostly autoicous, rarely dioicous; perichaetial leaves erect, lanceolate, gradually long-acuminate; margins sparsely serrulate, plane; costa short and double or none; cells linear to linear-flexuose, smooth or low-prorulose, thin- to firm-walled, becoming shorter and broader toward the insertion; alar cells sometimes differentiated in extreme angles. Seta elongate, smooth, reddish, twisted. Capsule horizontal to pendent, +/- arcuate, somewhat asymmetric, mostly ovoid to short-cylindric, usually with a differentiated neck, often constricted below the mouth when dry; exothecial cells quadrate to short-rectangular, the vertical walls firm, those of the cross-walls thin and wavy; annulus differentiated; operculum conic, mostly apiculate; peristome double, exostome teeth shouldered, bordered, on the front surface cross-striolate below, coarsely papillose above, trabeculate at back; endostome with a high basal membrane, segments keeled, perforate, about as long as the teeth, cilia in groups of 1--3. Spores spherical, finely papillose. Calyptra cucullate, mostly sparsely to densely hairy, rarely naked, smooth.


Species ca. 12 (1 in the flora): North America, Central America, West Indies, South America, Africa, Asia.


Chryso-hypnum is here defined by prostrate, soft plants with ovate leaves and cells that are prorulose at one or both ends. Other differences from Mittenothamnium, from which it is segregated (W. R. Buck 1984), are the nonstipitate plants, the shorter capsules with apiculate opercula, and the usually hairy calyptrae. Subsequent work by N. Nishimura and H. Ando (1986) has verified the value of segregating Chryso-hypnum from Mittenothamnium.


SELECTED REFERENCES  Buck, W. R. 1984. Taxonomic and nomenclatural notes on West Indian Hypnaceae. Brittonia 36: 178--183. Nishimura, N. & H. Ando. 1986. A revision of some Mittenothamnium species described from Mexico. Bryologist 89: 66--69.

1. Chryso-hypnum diminutivum (Hampe) W. R. Buck, Brittonia 36: 182. 1984.  F


Hypnum diminutivum Hampe, Linnaea 20: 86. 1847; Microthamnium diminutivum (Hampe) A. Jaeger; Mittenothamnium diminutivum (Hampe) E. Britton; M. thelistegum (Müller Hal.) Cardot; Ctenidium diminutivum (Hampe) M. Fleischer


Plants in dull, mostly pale- to dark-green, sometimes golden or brown-tinged mats. Stems to ca. 4 cm,; in cross-section with 2--3 rows of small thick-walled cells surrounding larger thinner-walled cells, central strand small, of thin-walled nodulose cells; axillary hairs with a single brown basal cell and a single relatively short hyaline distal cell. Stem leaves 0.8--1.2 mm, gradually and narrowly acuminate; costa unequal, one fork often ending 1/3--1/2 the leaf length; cells prorulose at distal and proximal ends abaxially, firm-walled; alar cells small, quadrate to subquadrate in 6--12 rows in the extreme basal angles. Branch leaves usually wide-spreading, sometimes more imbricate, lanceolate to ovate-lanceolate, 0.6--0.9 mm, gradually acuminate, concave; costa unequal, one fork often ending 1/4--1/3 the leaf length; cells linear to oblong-linear, conspicuously prorulose at distal and proximal ends abaxially, firm-walled; alar cells small, quadrate to subquadrate in 4--10 rows in the extreme basal angles. Sexual condition autoicous; perichaetial leaves triangular-lanceolate, 0.75--1.4 mm; costa often well developed, sometimes absent; cells smooth or low-prorulose at distal ends abaxially, firm-walled, becoming shorter, broader and thinner-walled toward the insertion; alar cells not differentiated. Seta 0.8--2.3 cm, twisted. Capsule 0.7--1.1 mm; annulus of 1--3 rows of elongate thick-walled cells, falling early; operculum conic-apiculate; endostome with a smooth or obscurely roughened basal membrane, segments finely papillose, cilia finely papillose, in groups of 1--2. Spores 11--19 \um. Calyptra naked or with a few hairs.


Common lowland weed, wide range of substrates, especially dead wood, mesic forests; 0--100 m; Fla., Ga., Ala.; Mexico; Central America; West Indies; n,c South America.


The often dense, soft mats of smallish, prostrate, subcomplanate-foliate plants with ovate leaves whose cells are prorulose at both ends will readily distinguish Chryso-hypnum diminutivum. It is extremely common throughout the West Indies and northern South America at all but the highest elevations, but barely makes it into North America. The species is widespread in tropical America, with many synonyms.